A spokesman for the Israeli embassy in Washington, Aaron Sagui, said Mr. Dermer didn’t launch a special campaign on Jan 21. Mr. Dermer, the spokesperson said, has “consistently briefed both Republican and Democrats, senators and congressmen, on Israel’s concerns regarding the Iran negotiations for over a year.” Mr. Dermer and other Israeli officials over the following weeks gave lawmakers and their aides information the White House was trying to keep secret, including how the emerging deal could allow Iran to operate around 6,500 centrifuges, devices used to process nuclear material, said congressional officials who attended the briefings. The Israeli officials told lawmakers that Iran would also be permitted to deploy advanced IR-4 centrifuges that could process fuel on a larger scale, meeting participants and administration officials said. Israeli officials said such fuel, which under the emerging deal would be intended for energy plants, could be used to one day build nuclear bombs. The information in the briefings, Israeli officials said, was widely known among the countries participating in the negotiations. When asked in February during one briefing where Israel got its inside information, the Israeli officials said their sources included the French and British governments, as well as their own intelligence, according to people there.